| Pollen formation in Lily - Microsporogenesis in Lilium |
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 | Microsporocytes in early prophase I.
The protracted prophase I is when crossing-over occurs. Much of prophase I consists of precise alignment of homologous chromosomes. |  |
| Mid-prophase I.
This stage is approaching pachytene, where the chromosomes are highly extended and paired homologous chromosomes exchange genetic material. |  |
 | Late-prophase I.
Homologous chromosomes continue to condense into their most compact forms as they near diakinesis. |  |
 | Diakinesis.
Diakinesis is the last stage of prophase I before metaphase. |  |
| Metaphase I.
This view shows metaphase chromosome assemblages both in longitudinal view and in polar view (end-on). |  |
| Anaphase I.
The homologous chromosomes have migrated to opposite sides of the cell, halving the genetic material. |  |
 | Telophase I.
A distinct layer of cell wall is laid down between the two phases of meiosis in lily. The phases in the second half of meiosis occur rapidly. |  |
 | Metaphase II.
The chromosomes undergo a separation of chromatids during the second half of meiosis in a cycle similar to mitosis (except for recombination between homologous chromosomes. |  |
| Telophase II.
Cytokinesis between the members of the tetrads is completed. Separation of the cells from the microsporocyte wall occurs soon after. |  |
 | Tetrads in the "callose special wall".
Callose forms around the entire tetrad within the old microsporocyte wall. Microspores separate from the megasporocyte wall, become round, and form a primexine -- a precursor template for later exine deposition. |  |
 | Tetrads completing the callose stage.
As microspores complete this stage, they elongate somewhat, becoming a bit football shaped. |  |
 | Released microspores.
At this stage, microspores have an exine (outer wall of sporopollinin) but are still filling with storage materials and remain pliable for a short time. | 
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| Microgametogenesis in Lilium |
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 | Bicellular pollen.
Generative cells are first formed in contact with the intine (inner pollen wall), but the cells then become immersed in the cytoplasm -- truly becoming "a cell within a cell". |  |
| The generative cell frequently is hooked, but always appears associated with the vegetative nucleus in a "male germ unit." The cytoplasm of the generative cell is dense and so it the generative nucleus, despite the non-motile nature of these cells. |  |
| Pollen Germination and Pollen Tube Growth |
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 | Pollen germination on the stigma.
When pollen lands on the stigma, it germinates and forms a pollen tube that continues to elongate until it penetrates the style, enters the ovary and then enters the micropyle and deposits sperm cells in a specific location within the embryo sac. |
